- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$string1 = "sqrtpdrt"; // matched
$string2 = "qwntfschrprtkjs"; // not matched (contains chr group)
var_dump(preg_match('/[bcdfghjklmnpqrstvwxz]{4}/i', $string1 ));
var_dump(preg_match('/[bcdfghjklmnpqrstvwxz]{4}/i', $string2 ));